Question for ladies who have awful first days

Today I start a new job. 3:30-11:30pm standing all day warehouse work, I am not in the best shape. I haven’t moved out of bed since 9am, I took medicine it didn’t help, I’m drinking water trying to eat. I don’t feel up to it today I’m in a lot of pain. I tried getting up and I feel like I’m gonna faint. The cramps go away for a second but when they come back they really hit me. Do I go into work and slack but still show up or call off and explain to them my situation and how I don’t wanna slack if I show up because of pain.